Knife assembly for rotary cutters



June 3, 1952 E. J. NEVIN KNIFE ASSEMBLY FOR ROTARY CUTTERS Filed Oct. 29, 1948 FIG.2.

. INVENTOR. EDWARD J. NEV/N W ATTORNEY Patented June 3, 1952 UNITED STATES PAT ENT OFFICE KNIFE ASSEMBLY FOR ROTARY CUTTERS Edward .L'Nevin, St. Louis County, Mo.

Application October 29, 1948, Serial No. 57,197

4 Claims. (Cl. 144230) This invention relates to improvements in knife assemblies for rotary cutters, and more particularly to improvements in the knife-and knifesupporting and positioning elements in and for the rotary cutter elements of woodworking machines and similar knife-bearing rotors of other equipment.

The general types of rotary cutter head w'fth which the present improvements are susceptible of utilization, are found in planers, jointers, machines for making wood molding, and numerous other items of similar equipment.

For many years it has been the custom in woodworking shops,.as the rotatable knife elements become dull from usage, to remove same, grind for sharpening, and replace each of the knives between an abutment and a follower element in the rotary cutting head. It is common knowledge that eachsuch grinding operation entails a cost, say within the range of two to threedollarslfor sharpening, and entails the further aggravated difficulty of lack of uniformity in setting of the knives. From this it resultsthat, in a threeknife rotor for example, that knife which is set farthest from the axis of rotation, becomes the sole working unit of the head, thus is dulled more quickly, creates an uneven operating condition, results in poor workmanship, and very importantly, creates in many cases an out-of-balance conditionof the rotary head. This latter .isobviously particularly aggravated and ofttimes destructive when the head is operated at high speeds, say at 3500 R. P. M. or :higher, depending upon the 'equipment'the'work to which it is subject, and other'factors. It is accordingly 9. major and general objective of the present invention to overcome, or at least to minimize the incidence of the stated shortcomingstof prevailing'woodworkingmachinea'arrd' greatlyto reducezthe cost-offmaintenance of cutting edges in a rotary cutter head .for :the general :purposes referred'to.

Statedconversely to the foregoing, an "importantobjective of the present improvements is automatically to provide-for an exactly even or uniformwsetup of the multiple knives ina cutter head, in suchwm'anner that all of the :knives'bear a virtually identical and. precision relation to the cutting rplane defined, for example, by a work table and the work thereon;

'Afurther highly important object of the presentsimprovements is realizedinaa virtually automatic assurance that the static and dynamic .balance of tthetrotary assembly will be maintained,

when once established, irrespective of installation of a new set ofcutting knives :or blades.

A still further valuable object of the invention is attained in a novel provision for adepthwise adjustment of a knife block in the recess therefor, thus enabling a precision adjustment-of the knife, with advantages aforesaid.

An additional, highly advantageous objective realized in a novel form of follower or pressure plate used for clamping the knife in operative position, and possessing a numberpf "advantages among which are to enable an accurate depthwise adjustment of the pressure plataincident to a similar setting of the knife holder or :block.

A still further object is realized in the provision of a cushioning abutment elementior 'the'knife. While such an element of itself provides'a better gripping engagement with the knife,:its function is best realized when utilized with the resilient follower heretofore referred to, andinithegeneral combination to which the improvements pertain.

The foregoing and numerous other objectives will more clearly appear fromthefollowing detailed description of a presently preferred embodiment of the invention, particularly when considered in connection with the accompanying drawing, in which:

Fig. 1 is an end elevation of a'knife assembly, as operatively mounted in a rotary cutter head for a woodworking machine, this'figuretshowing a fragmentary adjacent portion of a'cutter head formed of metal, which will be understood .as mounted for rotation about its axis;

Fig. 2 is a top or plan view of the cutter'assembly removed from the head, with parts broken away for clearness of illustration;

Fig. 3 is a view similar to Fig. l'but withthe blade removed, and pressure plate released;

Fig. 4 is an elevation in perspective of ,arrelatively thin metal knife element of oneitype suitable to be used with and as apart of the present improvements, and

Fig. 5 is a fragmentary section of a modified form of pressure or follower element.

Referring now by characters of reference to the drawing, it will be readily understood bythose familiar with machines of the type in present consideration, that the rotary cutter head, :indicated at CH, is in many cases provided .with'a series, usually three or four, evenly angularly spaced recesses, one of which is shown by 'Fig. 1, and bounded as later described. Itwill "be understood that the cutter head CI-I is Power driven and that the metal body of theihead is machined or otherwise formed to .provide the 3 recesses which are of open top form and of a generally rectangular section, each usually open at its opposite ends, and each defined by opposite side walls, 10, I l, and a bottom wall l2.

Although some of the features of present improvements are or may be susceptible of utilization without a knife holder or block, it is greatly preferred to utilize such a separate removable element, generally indicated at l3, in each of the recesses. Such a knife holder or block is machined so that it is characterized by a. planar face I4 which evenly engages and abuts the wall ID of the recess. Similarly, at a right angle to the surface it, is a planar bottom surface I5, and a smaller planar surface 16 constituting as such, or preferably as augmented by a cushioning insert I8 to be described, an abutment for one face of the knife or blade I? later to be described in more detail.

The opposite side of the knife is normally clampingly engaged by a follower or pressure plate generally indicated at 20, as will be later more fully referred to. The block I3 is further provided with a knife slot 2| receiving the currently unused inner edge portion of the knife I1, contemplated as being of thin, double-edge, double bevelled type, and along th knife slot 2| a surface 22 is bevelled, preferably to conform exactly'in slope, to such unused edge of the knife.

It'will be understood that the axial length of cutter heads for the types of service noted, may vary greatly, usually within a range from one inch to four or five feet in length, depending upon length of work table, service to which the machine is particularly adapted, and other factors. Accordingly, the length of each of the knife assemblies will correspondingly vary, and for this reason, it should now generally b stated that the numbers of certain of the screw and l lieu thereof, a thin, low cost cutting blade which,

by proper tempering and selection of alloys, may be produced to exhibit a longer life than conventional heavy gauge knives between grinding periods of the latter, and which may be made available to the trade at a cost less than such grinding operations. With this in view, it may be noted that the. knife I1 is provided with a double edge, and that each of its opposite edges is bevelled within a range of 30-45 the bevel being selected according to preference and type of service. Mention should also be made of the possibility and intention that blades of this general order may be produced for contour cutting, molding machines and the like, although for brevity the present description will be confined to knives provided with rectilinear cutting edges.

It is a preference that the opposite bevelled edges of each of the present knives be so ground that such edges lie in spaced parallel planes whereby, with the knife arranged and the bevel knife seat of the block sloped as shown by Fig. l,

.the unused edge 24 of the knife will be seated lfirmly upon the correspondingly sloped surface 2g f the block or holder l3. r'oceeding now. to a description of the follower or pressure plate generally indicated at 20, this latter is or may be formed of a resilient tempered metal for example, a tempered steel stock, and is of hollow form, and of a compressively resilient character. In the example shown, a top wall 25 may be continued downwardly below the rear shoulder of this wall, to form a rear wall 25. This latter is continued downwardly into a rocker portion 21 through an upturned portion 30, the latter being'formed t'o-have a hook-like engagement with a downwardly opening portion 3| extended along the adjacent edge of the block l3. It will appear from this arrangement that the follower 20 and the block 13 are so arranged that the follower may rock over a limited arc of movement upon this surface, but that, to assure against anycentrifugal displacement of the follower 20, the interfitting engagement of parts 27 and 33 provides in effect a pivoted connection, yet permits freedom of the aforesaid arcuate movement incident to takeup of the pressure plate or follower.

. In a tapered tail portion of the follower, the metal thereof is continued through a concave lower portion 32 which terminates in a plane below th outermost margin of portion 25.. These elements are connected by a plate 33, being that element which forms a clamping jaw engaging the knife, when the parts are operatively related.

Secured as by welding interiorly of and adjacent to the wall 26, is a series'of threaded members, which may consist of standard nutsas indicated at 34. Opposite each of nuts 34, the back plate 26 of the follower is apertured to receive a screw 35 the head of which abuttingly engages the wall H of the recess as screw 35 is threaded in a direction to bring the, plate 33 against the knife.

Although the described makeup of the follower or pressur plate exhibits the greatest resilience, it is preferred, in smaller units and when greatest economy is required, to form the pressure plate of solid construction. I In this form, in lieu of the nuts 34, tapped recesses 34A are employed for the reception of the clamping screws. In this somewhat modified form, shown by Fig. 5, the solid follower 20A is provided with a spring face element 33A. This face element may begiven a very slight curvature as shown, so as to exhibit a desirable depthwise resilience as the pressure member is brought into clamping engagement with the plate or knife 24. The face element 33A, may be considered as a bow spring. It may be attached as desired, for example by spaced tack welds along its top margin, as at 35A, leaving the lower margin of the spring member free to be displaced downwardly when forced up to the blade.

Referring now in more detail to the provision for depth adjustment of the knife holder and follower assembly within the recess, a preferred form of such provision consists of a plurality of threaded bushings 36 occupying and threadedly engaging the block, through the agency of threads in the bore 23. When the block is removed, such bushings may be selectively threaded inwardly or outwardly thereof so as to vary, with precision, the depth setting of the block or holder at various points along its length, within the recess. The bushing 36 being axially apertured, is normally occupied by a machine screw 40 threadedly engaging a tapped recess ll therefor in the block CH, and opening through the bottom wall or floor I2 of the recess. The screw 40 is provided with a fiat tapered head suitably kerfed, and the bushing 1'36z'is provided with diametrally opposite recesses 42 for the reception of a spanner or like, tool for adjustment. It will now be obviousthat when the exactly desired depth of the block or holder l3 for; the knife is arrived at, each of several bushings 36 is set accordingly, the block inserted in the recess, and the depth adjustment accurately maintained by-threading up the several screws 40.

Although the advantages and function of the several elements described are thought to have been apparent from the foregoing references to their several features, it may be noted for further completeness that, assuming the knife assembly to be removed from the recess therefor, the block or knife holder l3 may be inverted, and the several threaded bushings 35 accurately set with the aid of suitable gauge elements, such as a gauge block or the like, according to manufacturers recommendation. Prior to insertion of the knife assembly into the recess, the several clamping screws 35 are threaded inwardly of the follower a distance sufficient to provide full clearance for the knife l1, between the pressure plate of the follower, and the inset abutment element H3. The follower and knife having previously been removed, the knife holder or block I3 is set into the recess, and screws 40, the upper ends of which are accessible to a suitable screw driver or spanner, are tightened as far as possible. The follower may next be inserted by hooking the tail portion thereof beneath the overlying ledge 3! of the block, the knife I! now inserted in final position with its unused edge 24 bearing against the correspondingly sloped seat 22. Following this, the several screws will be threaded out of the follower plate to bring their respective heads into firm abutting engagement with the upper portion of wall II of recess. The knife assembly is now securely positioned in the recess, ready for operative rotation of the cutter head CH.

Inasmuch as the knife I1, after a period of use, may have its edges reversed for better cutting action on the work, the several knives of the assembly are removed by threading in the several screws 35 to release the knives, the originally unused edge of each is brought to active cutting position, and the clamping screws again threaded to secure the knives in place. The replacement of knives, as contemplated, rather than the resort to grinding operations, is recommended to be done by substituting complete sets of such knives at a given time.

It will now have appeared that it will usually be unnecessary for long periods of time to effect any change in the depth adjustment of the knife holder or block l3, as through bushings 36, but that, if and when such adjustment is required, it may be easily and precisely effected so as to bring all of the operating edges of the several knives in exactly the same plane, being the plane or the work or slightly therebeyond.

A valuable feature, in service, consists of the relatively soft inset element 18, which may consist of brass, fiber or other cushioning material. Used with a solid follower, the element [8 augments the gripping action on the blade, absorbs shocks and vibration, and reduces the incidence of blade or knife breakage. These advantages are obtained in substantial degree by the resilient follower, and in yet greater degree by both features of improvements.

The several knives H are produced with sufficient uniformity and accuracy that the substitution of new knives for dulled cuttingiunits. will preserve a nicety of both static and dynamic balance of the entire rotating mass of the cutter head. Similarly, the several knife assemblies for use in a given cutter head, are preferably dispensed in matched sets. in which each of the corresponding elements are accurately balanced as to mass, thus minimizing the likelihood of any out-of-balance condition.

It will now have appeared that the assembly as described attains each of the several objectives 3 above expressed, as well as many other advantages implied from the foregoing description.

Although the invention has been disclosed by detailed reference to the several component parts, the detail of description should be understood in an instructive rather than in any limiting sense, numerous variants being possible within the scope of the claims hereunto appended.

I claim as my invention:

1. In a rotary cutter head provided with a recess for a knife assembly, a knife supported so as to extend into said recess, an element carried by the cutter head and providing an abutment for one side of the knife, and an inverted, substantially L-shaped follower of a resilient character, and normally abutting the opposite side of the knife, a pair of coacting, detachably interfitted, pivotally related bearings carried. respectively by the said element and the follower, and screw threaded means, coacting with the follower for releasably clamping the knife between said follower and abutment.

2. In a rotary cutter head for a woodworking machine or the like, the head being provided with a recess for a knife assembly, a knife assembly in said recess, including a block, a pressure plate, a knife engaged by the pressure plate, and screw threaded means coacting with the pressure plate for releasably clamping the knife between said pressure plate and block, the .pressure plate and the block being formed to provide interfi tting projections and adjacent recesses, resulting in a quick-detachable pivotal connection of elongate hook form, the projections being of rounded section and thus providing for rocking movement of the pressure plate on the block incident to clamping adjustment of the pressure plate.

3. In a rotary cutter head for a woodworking machine or the like, and which is provided with a knife recess, a knife assembly in said recess, in cluding a block providing a knife abutment, a knife normally having one face adjacent said abutment, a follower plate engaging the opposite side of the knife, means for releasably clamping the knife between said follower plate and abutment, a depthwise bore in the block, a threaded bushing in said bore and depthwise adjustable therein by virtue of its threads, and a clamping screw extending through said bushing and having threaded engagement with the cutter head in the bottom of the recess.

4. In a rotary cutter head for a woodworking machine or the like, the head provided with a recess adapted to receive a knife assembly, a knife extended along said recess, an insert of a relatively soft non-ferrous metal, providing an abutment for one side of the knife, a compressively resilient pressure plate engaging the opposite side of the knife, means providing a pivot of elongate hook form for the resilient pressure plate in adjusting movement of the plate toward and from the knife, and screw thread means for actuating the pressure plate to effect a clamping engagement; of the knife between the pressure plate and said abutment insert.

EDWARD J. NEVIN.

REFERENCES CITED Number The following references are of record in the file of this patent: 10 Numbel 8 UNITED STATES PATENTS Name Date Wells Apr. 6, 1886 Shimer Dec. 24, 1907 Perkins et a1 Jan. 19, 1909 Watkins July 16, 1912 Bunch June 11, 1918 FOREIGN PATENTS Country 7 Date Great Britain Apr. 16, 1931 

